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Full text of "Text Book Of Mechanical Engineering"

Expanding Mandrel.

155

the key as shewn at K ; and, finally, the worm end of the spindle
is used, as at L, for large drills. As the worm only bears on j in
one direction, it is applied at the opposite hole M to release the
drill.

Chucks that are either independent^ universal^ or eccentric at
will, are also made, having combinations of the foregoing motions.

Expanding Mandrel.—There is still another plan of
support for work having a hole through its centre. It is fixed on
a mandrel (or spindle that can be centred in the lathe), of which
several sizes are kept, having a slight taper, one suitable for the
work being chosen; but a more expeditious tool is the expanding
mandrel in Fig. 154. The mandrel proper is coned at A, and
has three grooves of the same inclination as the cone, in which

ride keys so tapered that their outer surfaces form portions of one
cylinder. The mandrel is screwed with right and left hand
threads as shewn, and the advance of nut B will push the bars
cc up the incline, so expanding the cylinder to any diameter
within the limit of the tool 0 serves also as carrier for the work,